The Autistic BrainUnderstanding how differences in brain structure may influence autism

by Carrie Bishop

May 01, 2014

Kids with autism are different from their neurotypical peers. That much is known. But what is it that makes autistic kids autistic? What is different about these kids’ brains versus other “typical” brains?

Dr. Thomas Lock, a developmental pediatrician with Riley Hospital for Children at Indiana University Health, says there are several observations on how and why the autistic brain works the way it does, yet no definitive ideas. What has been seen is that brains in children with autism tend to be larger and the cell connectivity is often disorganized.

Scientists have used functional magnetic resonance imaging (fMRI) to look at autistic brains and have found that there are aspects of the brain that do appear different in individuals with autism. Yet, Lock says they are not so different that one could take a single scan of a single brain and say it’s the brain of a child with autism. On average, he says, there are frontal lobe differences that can affect executive functions, such as planning, organizing, strategizing and managing time.

“The fact that you can see it’s different is important, but it may not be a good predictor of what the symptoms are going to be because so much else is going on in the brain...If you have one child with autism, the probability of having a second child with autism is elevated. But the probability of having a child with ADHD is also elevated,” said Lock. This is because many factors come into play with autism, like genes, that affect how its symptoms present.

In fact, Lock says there are many sites in the genome that are associated with autism, be it deletion or duplication of chromosomes that are associated with the disorder’s symptoms. “The problem is those same sites pop up in studies in ADHD or language disorders or bipolar or schizophrenia, so they are not as specific as we’d like them to be,” he said.

It’s easy to see the complexity of autism. So far, more than 800 genes are associated with it and scientists don’t understand yet what all these genes are doing. The disorder is essentially a collection of symptoms and individuals can come to these symptoms from any number of paths.

“It’s like, how do you get to Chicago from here? Each one of those routes is a pathway that might lead to autism. Some are common and some are different,” said Dr. Martin Plawecki, child psychiatrist and medical director of the Riley Christian Sarkine Autism Treatment Center at Indiana University Health.

Plawecki says the architecture of autistic children’s brains tends to be disturbed, meaning its cells can be disorganized. A recent study by scientists at the Allen Institute for Brain Science in Seattle and the University of California at San Diego School of Medicine helps explain the disorganized structure. They examined post-mortem brain tissue samples from individuals age 2 to 15, half of whom had autism. As part of the study, the lead author created the first 3D model showing brain locations where patches of cortex failed to develop normally, according to online reports. The researchers believe this disruption of cell development likely occurred in the second and third trimesters, a time in fetal life when the brain sets up neural cell types, neural connections and neural layers. What causes the disruption remains the question.

So how does this all translate to treatment and everyday life for kids with autism? It doesn’t. Not yet anyway. The best treatment, according to experts, remains behavioral therapy to teach kids with autism how to respond to their environment. As families continue down this practical path, the scientific community will also continue its search for answers about the autistic brain.